Task Reload Scenario Query

[Wodge]

Hello!

If I have multiple tasks setup so that one runs after the other, for example:

1. Task 'A1' runs first every 15 minutes.

2. Task 'A2' has a trigger to run after 'A1' successfully finishes.

3. Task 'A3' has a trigger to run after 'A2' successfully finishes, but 'A3' takes a lot longer to finish reloading so 'A1' starts to load again before 'A3' finishes the initial reload.

Will multiple reloads be queued up for the third task? How does QlikView handle this scenario?

[JandreKillianRIC]

Hi @Wodge 

I think with QlikView you need Publisher to accomplish this. (The correct wording is Task Chaining). 

Unfortunaly I don't have access to a QlikView site to verify this so this might actually only need QlikView. 

For task 1 I will also add a additional check (Task Chaining) to see if Task 3 has reloaded successfully. 

[Chip_Matejowsky]

Hi @Wodge,

If task A3's trigger is dependent upon the successful completion of task A2, then it will only tirgger when A2 successfully completes. Refer to QlikView Help entry Task Dependencies which states: Task dependency is a way of making sure that the current task runs only if other tasks have finished their last execution successfully. The task dependencies overrule any trigger, which means that a trigger might not be able to start the current task, if a task dependency for the current task is not fulfilled.

In your scenario, suggest that you schedule task A1 to trigger on the successful completion of task A3, or schedule task A1 run every X minutes, giving ample time for tasks A2 and A3 complete.

Best Regards

[Wodge]

Hi Chip,

Thank you for that, I had a look at Task Dependencies and it is something I am looking to implement.

What I am looking to confirm is whether Task A3 gets queued up every time Task A2 finishes. So for example:

1. Task A1 Reload finishes successfully. 

2. Task A1 finished, Task A2 is started and is also successful. 

3. Task A2 finished, Task A3 is started but isn't finished yet.

4. 15 minutes have passed,Task A1 is started and finished.

5. Task A1 is finished, Task A2 is started and finishes.

6. ?

Step 6 is the problem, what happens at that stage? Does QlikView queue up Task A3 however many four times every hour? or after 15 minutes pass, Task A1 is started again whilst completely skipping Task A3?

Best regards,

[Chip_Matejowsky]

For step 6, if Task 3 is dependent upon the successful completion of Task 2 and Task 2 successfully completes, then Task 3 will start as it's trigger has been fulfilled. Task 3 doesn't know about Task 1's "run every 15 minutes" schedule. 

Best Regards

[Wodge]

Hi Chip,

Thank you for that, although I'm afraid I may not be explaining this that well.

I understand that Task 3 will wait on Task 2, but if Task 3 is running, and Task 1 starts up again and finishes, which then starts Task 2, then what happens once Task 2 finishes?

You see its a bit of a deadlock situation, because Task 3 is running (as the trigger was successful, i.e. Task 2 finished), but then Task 2 is started again, so what happens in that instance?

Please let me know if that makes sense!

Best regards,

[Chip_Matejowsky · Accepted solution]

You see its a bit of a deadlock situation, because Task 3 is running (as the trigger was successful, i.e. Task 2 finished), but then Task 2 is started again, so what happens in that instance?

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Task 3 would be triggered again at the succesful completion of Task 2. Even though an earlier iteration of Task 3 is still running. The task may fail due to the app being in use, but it would still trigger. 

Best Regards

[Wodge]

Hi Chip,

Thank you for the clarification!

Best regards,